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Can I constrain an object to a compound curve

Creator
Creator

I'm trying to constrain a curved arm with multiple radii to slide along two pins, but I can't seem to be able to constrain the model in such a way that the pins correctly track the curve of the arm, neither in the Modeling nor Motion applications. I've seen a video of a cam-and-follower assembly, which seems very close to what I need, but so far I haven't found the combination of constraints (or some other function) to make it move correctly. (And it's not that there are two pins...I couldn't make it work with one pin either). In Modeling, I can constrain the pins to one of the curves, but not the other two. 

 

I've included a pic of the model. I would love some guidance!

10 REPLIES 10

Re: Can I constrain an object to a compound curve

PLM World Member Phenom PLM World Member Phenom
PLM World Member Phenom

I think you will need to create a curve in the center of the slot and then "Join" that into a single curve.  You shuld be able to constrain to the joined curve.

John Joyce, Manufacturing Engineer,
Senior Aerospace

NX 11.0.2.7 Vericut 8.0.3 - Statements and opinions are mine alone and do not reflect
the opinion of my employer or any other member of the human race

Re: Can I constrain an object to a compound curve

Siemens Phenom Siemens Phenom
Siemens Phenom

Hi @clbrgess 

Refer the other post "Cam constraint"

Re: Can I constrain an object to a compound curve

Siemens Phenom Siemens Phenom
Siemens Phenom

@clbrgess 

As the link @GaneshKadole  posted shows, if you define a composite spline from the center path of the slot and 2 points along the axis of the bosses, then you can apply an 'align' constraint between each point and the center path of the slot.

Take a look in the movie below:

(view in My Videos)

Regards,
Abe

Re: Can I constrain an object to a compound curve

Creator
Creator

@Abeinjapan That's exactly what I need it to do! But forgive me, I'm having trouble getting the spline in place correctly (I've never used them before). I did 3 separate [studio] splines, each 3 degrees, and through points that were placed between the ends and midpoints of the edges of the slot (using "Between Two Points"). But the spline for the middle radius doesn't match the curve of the slot, and for the life of me I can't work out why, or how to fix it.

 

Could you tell me how you made your spline?

Re: Can I constrain an object to a compound curve

Creator
Creator

Thanks @joycejo. I'm fairly inexperienced with this level of NX 12, how would I go about creating a curve that constraints would recognize?

Re: Can I constrain an object to a compound curve

Siemens Phenom Siemens Phenom
Siemens Phenom

@clbrgess 

The way to create the spline is to use a 'composite curve' with the 'join' option. Within the composite curve command, select the original arcs you created and make sure that join is set in the dialog. The resulting spline shape will be within the defined tolerance from the original shape.

Regards,
Abe

Re: Can I constrain an object to a compound curve

Creator
Creator

@Abeinjapan
When I try to select the arcs in 'composite curve' with or without 'join curves (general)' selected, all of the edges of the slot are automatically selected at once, and in the part navigator it reads 'Composite Curve (28)' and nothing else happens. I noticed in your video that it read 'Composite Curve (3).' If I understand your last reply, it seems like a) I should be able to select the individual different radius curves, and b) that a spline will automatically be created. Am I just misunderstanding?

 

I wonder if the way that I constructed the arcs is causing a problem? I can't imagine how...it was just a bunch of circles in sketch.

 

(And by the way, I really appreciate you walking me through this.)

 

comp curves.png

Re: Can I constrain an object to a compound curve

Siemens Phenom Siemens Phenom
Siemens Phenom

@clbrgess , I used Offset Curve instead of Composite Curve.

 

Applied constraints successfully, but unable to move Slider using Move Component. Attching the part files.

 

(view in My Videos)

Regards,
Samadhan

GTAC | NX Help: NX1102 | NX1202 | NX1847
Please mark post as an "Accepted Solution", if it answers your question/is more helpful!

Re: Can I constrain an object to a compound curve

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

@clbrgess wrote:


When I try to select the arcs in 'composite curve' with or without 'join curves (general)' selected, all of the edges of the slot are automatically selected at once, ... If I understand your last reply, it seems like a) I should be able to select the individual different radius curves, and b) that a spline will automatically be created. Am I just misunderstanding?

 


Pay attention to the curve selection rule in effect; it sounds like the rule "tangent curves" was active during your selection. Try changing it to "single curve" and note how you can select individual curves. To get the centerline spline, I'd suggest creating a composite curve (using single curve selection) then using offset curve to move it 1/2 of the slot width.